CXCR1/2 blockade to enhance response to immune checkpoint inhibition in an aggressive orthotopic pancreatic adenocarcinoma model.

Abstract

19 Background: Pancreatic adenocarcinoma (PDAC) is the fourth leading cause of cancer related deaths, with the incidence expected to rise in the coming years. Despite conventional chemotherapy and advances in immune checkpoint blockade, 5 year survival remains a dismal 8%. Intratumoral accumulation of granulocytic myeloid derived suppressor cells (G-MDSC) pose a significant barrier to treatment as they contribute to immune evasion by PDAC and correlate with poor prognosis. The ELR+ CXC chemokine receptors CXCR1 and CXCR2 (CXCR1/2) contribute to peripheral neutrophil migration into tissues and have been implicated in tumor mediated G-MDSC recruitment to the tumor microenvironment. Here we present our findings using an orally dosed CXCR1/2 inhibitor, SX-682, in an orthotopic PDAC model. Methods: C57BL/6 mice underwent orthotopic injections with KP2 cells. Mice were randomized into five groups (Table) receiving three weeks of FOLFIRINOX with combinations of SX-682 and/or checkpoint inhibition (anti-PD1/anti-CTLA4). FOLFIRINOX was dosed weekly for three weeks. Checkpoint inhibition was administered twice weekly. Chow weights were monitored for consumption of SX-682. Results: The simultaneous administration of FOLFIRINOX with SX-682 combined with checkpoint inhibition (triple therapy) resulted in a significant increase in survival compared to other groups (p = 0.0001). Notably, there was a significant increase in survival with triple therapy versus FOLFIRINOX plus checkpoint alone (p = 0.0259). Median survival of the triple therapy group was 42.5 days, compared to 37 days with checkpoint inhibition (p = <0.05). There were no differences in chow consumption between the control and medicated chow groups. Conclusions: CXCR1/2 blockade combined with immune checkpoint inhibition and first line chemotherapy significantly enhanced survival in our PDAC mouse model. Thus, CXCR1/2 inhibition with SX-682 represents a promising target for clinical intervention in PDAC. [Table: see text]